Metal sheet and strip flattening apparatus



June 20, 1967 c. GUILLOT 3,326,025

METAL SHEET AND STRIP FLATTENING APPARATUS Filed July 6, 1964 3 Sheets-Sheet 1 June 20, 1967 c, Gu o 3,326,026

METAL SHEET AND STRIP FLATTENING APPARATUS Filed July 6, 1964 3 Sheets-Sheet 2 June 20, 1967 c. GUILLOT METAL SHEET AND STRIP FLATTENING APPARATUS Fild July 6, 1964 3 Sheets-Sheet 3 United rates atent fiFice 3,326,626 METAL ESHEET AND STREP FLATTENIN G AlPARATUS Claude Guiiiot, LHorme, France, assignor to Compagnie des Ateliers et Forges de la Loire St. Chamontl, Firminy, St. Etienne, Jacob-Heitzer, Paris, France Filed Juiy 6, 1964, Ser. No. 386,226 Claims priority, application France, Aug. 1, 1963, 943,447, Patent 1,372,009; 943,448, Patent in (Zlairns. or. 72-163) This invention relates broadly to apparatus for leveling and flattening rolled sheet and strip stock and for removing the deformations that are induced therein as a result of the rolling operations to which the stock was exposed.

Metal sheet or strip on issuing from a rolling mill usually presents distortion due to the more or less random residual stresses introduced into the metal by the elastic and plastic deformations induced therein during the rolling operations. Such distortion often takes the form of so-called stretcher strains or Liider lines, also sometimes known as orange peal, and manifests itself mainly as waviness of the strip or sheet in the longitudinal direction. Various means are used to eliminate this defect, an especially convenient method which is frequently used being that known as roller leveling, in which the rolled strip is passed through a succession of bending rolls of small diameter staggered longitudinally and arranged to impart alternate up and down flexing to the strip as it is fed through the roller leveler. So-called stretcher leveling is also used.

Roller leveling and equivalent treatments are effective to remove the longitudinal distortion or waviness from rolled sheet and strip. Very often however, it is found that such treatment has substituted this original defect by another. That is, the roller-leveled or similarly treated sheet frequently presents transverse distortion in the form of a continuous transverse camber, whereby the strip when in free relaxed condition assumes the appearance of an elongated trough. Admittedly this defect is less objectionable than the longitudinal waves or stretcher strains which it replaces, since after the sheet or strip has been cut longitudinally into narrower strips or bands, as is required in many applications, the resulting narrow strips are comparatively flat. However, in various cases such transverse camber is objectionable, and it is a principal object of the present invention to eliminate this particular defect. Broader objects of the invention include the provision of improved methods and means of producing rolled sheet and strip stock having superior flatness, surface condition and freedom from objectionable internal strains.

The invention will now be described in greater detail with reference to the accompanying drawings, given for purposes of example and illustration but not limitation, and wherein:

FIG. 1 is a somewhat simplified view in vertical cross section longitudinally of the strip, of flattening apparatus according to an embodiment of the invention;

FIG. 2 is a schematic view on a smaller scale, illustrating how the apparatus of FIG. 1 is utilized according to an aspect of the invention in imparting controlled elongation to steel strip prior to coiling the strip; and

FIG. 3 similarly illustrates another use of the invention in which the improved flattening device is applied to strip issuing from a final coldworking or temper-rolling pass and prior to being taken up in a coil.

The invention is based on the finding that the transverse distortion occurring in sheet stock issuing from a roller-leveler or similar conventional device and tending to impart the shape of a longitudinal trough to the sheet, is due to the fact that the sheet or strip, in passing through the ultimate roll of the roller-leveler or equivalent device serving to impart alternate flexing to the sheet, has a pattern of differential transverse stresses set up in it, the stresses varying over the depth dimension of the sheet. This in turn is due essentially to the fact that at the surface of the strip engaging the surface of such ultimate leveler roll, friction forces prevent any substantial variations in the width of the strip.

More specifically, if the longitudinal and transverse coordinates of the strip are designated by x and y respectively, then the unit deformations or strains and 6,, along the respective coordinate directions x and y at any point of the thickness dimension of the strip are known to be related to the stresses s and s along said respective directions by linear equations of the forms 1 1 add twhere E( is an elasticity modulus.

At the contact generatrix between the strip and the roll, the unit transverse strain =0 owing to friction, and hence at said generatrix we have from Equation (2) s /2s At the corresponding position on the opposite face of the strip the transverse stress s is substantially zero, whereby it will be evident that across the thickness dimension of the strip there exists an increasing gradient of transverse plastic stresses from the outer or free face of the strip to the face engaging the last leveler roll. On issuing from this roll, the sheet must therefore assume an equilibrium configuration in the form of a trough whose concavity is directed towards said roll.

According to the present invention this condition is overcome through the provision of an additional or corrector roll of small diameter positioned beyond said ultimate leveler roll and arranged to be engaged by the face of the strip remote from the face thereof that was engaged by said ultimate leveler roll. Means are further provided for forcing the sheet into engagement with the corrector roll and for adjusting the position of the corrector roll in a direction normal to the sheet whereby the adjustment can be so made that said corrector roll will set up in the sheet as it is fed therepast differential transverse stresses in a pattern generally reverse from that of the stresses set up by the ultimate leveler roll, and such that the combined stresses generated by both said rolls will create a resultant extending substantially through the mid-point of the thickness dimension of the strip, thereby canceling out the transverse distortion and producing a strip that will be flat and level both in the longitudinal and the transverse directions.

Referring to FIG. 1 of the drawings, the flattening apparatus there shown comprises a frame including in the exemplary embodiment upper frame plates such as 8 and lower frame plates such as 25 arranged in a common general vertical plane, and the vertical spacing between said plates is preferably made adjustable as shown through the provision of replaceable spacer shims such as 30 and 31.

A metal strip to be flattened illustrated as the dotdash line 1 is assumed to be fed continuously in the leftward direction indicated by arrow F and is held under tension through suitable means not shown in FIG. 1 and later described. Such means may assume the form e.g. of the tensioning blocks T1 and T2 shown in FIG. 2 and the apparatus illustrated in FIG. 1 may be assumed to be positioned between the tensioning blocks T1 and T2 of FIG. 2.

The apparatus includes a roller-leveler section which comprises the pair of small-diameter leveler rolls 2 and 2' mounted respectively below and above the path of sheet 1 and in longitudinally offset relationship so as to flex the sheet 1 downwardly and upwardly as shown. Each leveler roll 2,2 is mounted in cradled relation in a pair of larger-diameter supporting rolls 4 and 4' for the lower leveler roll 2, and 3 and 3' for the upper leveler roll 2. The uppersupporting rolls 3, 3 are rotatable on shafts 5, 5' fixedly secured by means of the bolted cradles shown in supporting blocks or hearing supports 6 secured with screws 9 to brackets 7 which in turn are secured to the upper mounting plates 8 by means of bolts and cotter-pinned nuts 11. A locating key or shim 10 is shown interposed in registering grooves of the bracket 7 and the block 6.

The lower supporting rolls 4, 4' are mounted from the lower mounting frame plates 25 in a manner exactly comparable to the mounting means just described for the upper supporting rolls, including the supporting blocks 13, and bracket 14 secured to the lower frame plates 25 by means of'bolts and nuts 15.

The strip 1 on issuing from the last roll 2' of the roller-leveling device just described is substantially flat in the longitudinal direction but will generally show transverse distortion in the guise of a continuous throughlike camber, as earlier explained. Accordingly, in the flattening apparatus of the invention the roller-leveling section including rolls 2 and 2 is followed by a cambercorrecting section now to be described. This correcting section includes a director roll 16 of relatively large diameter, mounted above the sheet 1 and journaled in suitable bearings not shown, carried in bearing supports or blocks such as 19 secured tothe upper brackets 7 by way of screws 20 with the interposal of a locating key 21. Beyond the roll 16 the sheet 1 is passed over a smalldiameter corrector roll 17 engaging its under face, i.e. the face thereof remote from the face which was engaged by the last roll 2' of the leveling section.

It should be made clear at this point that the largediameter director roll 16 serves to direct the sheet and form it into engagement with the corrector roll 17 but does not otherwise play an essential part in the cambercorrecting process of the invention. Said director roll 16 may in fact in many cases be omitted.

The camber-correcting roll 17 is mounted in rolling engagement with a pair of larger-diameter support rolls 18, which are journaled in bearing blocks such as 23. The bearing block 23 is supported from the lower frame plate 25 through adjustable supporting means whereby the position of the support rolls 18, 18' and hence the position of camber-correcting roll 17 in the direction normal to the sheet 1 can be accurately adjusted. For this purpose the supporting block 23 is secured, e.g. screwed, to a wall of a bracket 22 which has a lug extension pivoted on a sturdy pivot 24 extending across the frame. Excenter means are provided for adjusting the position of bracket 22 about pivot 24 and includes a cam disc 26 secured in excentric relation on a shaft 27 and peripherally engaging an accurately machined plate or strip 29 secured with screws such as 29 to a wall of bracket 22. Control means not shown are provided externally of the apparatus for accurately adjusting the angular position of shaft 27 and cam disc 26 and hence the positioning of bracket 22 and of support rolls 18, 18' and corrector roll 17 normally to sheet 1.

It will be understood that by way of the adjustment just described the position of corrector roll 17 can be so adjusted with respect to that of the output leveler roll 2' normally to the strip, that the corrector roll will generate transverse stresses in the strip in a pattern such that, when superimposed over the pattern of transverse stresses generated by said leveler roll, over-all the resultant of the stresses will extend through the mid-point of the thickness dimension of the strip, thereby cancelling out the transverse distortion or camber in the strip as earlier explained.

In FIG. 2, the flattening apparatus of the invention is shown applied in conjunction with means serving to impart controlled elongation to a strip fed in the leftward direction F prior to being coiled up on reeling means not shown. The installation comprises a pair of sets of tensioning rolls T and T between which is interposed a flattening apparatus according to the invention generally designated C, and generally similar to the apparatus shown in FIG. 1, with similar references being used to designated corresponding parts. The output set of tensioning rolls T may be motor driven and is mechanically coupled to the input set of tensioning rolls T through kinematic means such that the linear velocities V and V of the rolls in the respective sets T and T are related by the equation:

v =A percent where A percent is the constant elongation to be imparted to the strip 1. The aforementioned kinematic coupling between the sets of input and output tension rolls T and T may be any suitable adjustable device, such as a gearbox, a differential gearing or other speed variator capable of providing a preferably continuous range of elongations.

The flattening apparatus C as described with reference 1 to FIG. 1 includes a leveler section here designated R and including a pair of leveler rolls 2, 2' with their associated support rolls 3-3 and 4-4, serving to impart alternate flexion to the strip, and a camber-correcting section R comprising a director roll 16 and a corrector roll 17 with its associated support rolls 18, 18. The corrector roll 17 engages the opposite face of strip 1 from the face engaged by the ultimate roll 2' of the leveler section.

The system illustrated in FIG. 2 effectively imparts to the strip 1 a controlled elongation and alternate flexing or leveling which removes'the stretcher strains from the strip and imparts the desired elongation thereto without affecting the surface condition of the sheet or strip stock. With all of the rolls used being mounted in accurately parallel relation, there is produced a thorough equalization of the lengths of all the elementary longitudinal fibres of the strip whereby a perfectly flat and planed condition can be subsequently obtained in the sheet. The diameters of the leveler rolls 2 and 2 should be selected in view of the gauge thickness requirements in the sheet and the range of elongation desired, so as to avoid in all cases imparting to the section of the strip between the input tensioning rolls T and the leveling section R a traction stress exceeding the elastic yield limit of the metal liable to induce the formation of Liider lines therein. A range of diameters usually found suitable for the rolls 2 and 2' is from 30 to 40 mm.

The camber-correcting section R as earlier explained serves to remove the transverse camber which tends to be induced in the strip 1 on issuing from the leveling section R which camber has its concavity directed towards the last leveler roll 2', i.e. upwardly in the embodiment shown. The camber-corrector sectiongR which includes the rolls 16, 17, 18, 18 as above described removes said residual transverse camber and provides a final sheet or strip stock which is flat and level in all directions. As explained above it is necessary in order for this purpose to be achieved that the position of the corrector roll 17 normally to the strip 1 be accurately adjustable and for this purpose the support rolls 18 and 18' are adjustably mounted preferably by means of the excentric adjusting mounting device described with reference to FIG. 1, and omitted from the showing of FIG. 2 for clarity.

In FIG. 3 the invention is shown applied to a system in which a strip 1 is passed through a final cold-working or temper rolling pass in a rolling mill generally designated 33 prior to be taken up in a coil 32.

Even though the reduction of the sheet in such mill is quite low, usually of the order of 1%, the rolling stresses are high and produce high residual stresses in the metal. Due to these stresses, the sheet assumes a shape of equilibrium where it is substantially distorted, and moreover, if subsequently cut, the shape of the sheet will change because of the change in the stress distribution pattern produced by the cutting operation. Thus, when a broad strip is cut into narrower strips the latter may be distorted even if the initial strip was substantially flat. To overcome this between the rolling mill 33 and the take-up coil 32 there is interposed a flattening device according to the invention which again may be similar to the one described in detail with reference to FIG. 1, and Will not be described again. Parts of the flattening apparatus have been designated with the same reference numbers as the corresponding parts in FIGS. 1 and 2. It will be noted that on issuing from the corrector roll 17 of the apparatus, the strip is passed under a deflector roll 34 which serves to cancel the influence of variations in radius of the coil 32 on the vertical position of the strip and hence the pressure exerted by corrector roll 17.

The system just described with reference to FIG. 3 has a number of specific advantages. It is economically advantageous since no special means need be provided for feeding and coiling up the strip over and beyond the means already provided in connection with the rolling mill. It should further be noted that the strip issuing from the final cold-working pass in mill 33 is inherently subjected to high residual stresses. Hence it is at this time in an especially suitable condition for readily taking plastic deformation. With time, the stresses would be relieved somewhat. It is when the internal stresses in the meta-l are particularly high, as is the case directly at the output from the cold-working mill 33, that the plastic deformations involved in the flattening process of the invention have their greatest effectiveness and are easiest to perform.

The invention is useful in performing so-called skinpass cold-working treatments without impairing the surface condition of the metal stock by the combined action of alternate flexing of the sheet and controlled elongation whereby the degree of cold treatment and hence the duration of the longitudinal flattening effect can be accurately controlled. Further, such skin pass operations or continuous flattening operations may be performed in cases where the desired feed velocity exceeds the maximum velocity permitted by the flattening apparatus. This aspect of the invention was described in detail with reference to the embodiment of FIG. 2.

It will be understood that the invention may be embodied in apparatus and applied to specific purposes other than those explicitly described and illustrated herein, and that its scope should consequently not be interpreted as limited otherwise than as required by the terms and spirit of the ensuing claims.

What is claimed is:

1. A metal strip and sheet stock flattening apparatus having means for feeding the stock longitudinally under tension comprising a set of at least tWo leveler rolls disposed transversely of the stock and engaging opposite faces thereof in longitudinally displaced positions to impart alternate transverse flexing to the stock for removing longitudinal distortion therefrom, a corrector roll disposed transversely of the stock beyond the last leveler roll of said set engaging the face of the stock remote from the face engaged by said last leveler roll, means for adjusting the position of said corrector roll in a direction normal to the plane of the stock to set up differential transverse stresses over the thickness dimension of the stock in a pattern substantially reverse from the pattern of transverse stresses set up by said last leveler roll to cancel the transverse camber that tends to be imparted by said last leveler roll to the stock.

2. A flattening apparatus as defined in claim 1 wherein a pair of support rolls of larger diameter than said corrector roll support and engage said corrector roll.

3. A flattening apparatus as defined in claim 1 wherein a director roll of a greater diameter than said corrector roll engages the stock ahead of the corrector roll on the face thereof opposite that engaged by said corrector roll.

4. A flattening apparatus as defined in claim 2 wherein position-adjusting means are provided for adjusting the position of said support rolls towards and away from said stock.

5. A flattening apparatus as defined in claim 4, wherein said position-adjusting means comprises bracket means journalling said support rolls, means mounting said bracket means for pivotal movement about an axis parallel to that of said rolls, and eccentric means for adjusting the angular position of said bracket means about said axis.

6. Strip and sheet stock flattening apparatus comprising in combination means for longitudinally feeding said stock; at least two leveler rolls disposed transversely of the stock engaging opposite faces thereof in longitudinally displaced positions to impart alternate transverse flexing to the stock; support rolls of a greater diameter than said leveler balls engaging each of said leveler rolls on the sides thereof directed away from said stock; a transversely-disposed director roll of relatively large diameter engaging the stock on the same face thereof as that engaged by the output one of said leveler rolls; a transversely-disposed corrector roll of smaller diameter than said director roll engaging the stock on the opposite face from that engaged by said director roll; a pair of support rolls cradlingly engaging said corrector roll on the side thereof directed away from the stock; and means for adjusting the position of said last named support rolls and said cor rector rolls towards and away from said stock.

7. An apparatus as defined in claim 6, wherein said position-adjusting means comprises bracket means journaling said second-mentioned support rolls, means mounting said bracket means for pivotal movement about a transverse axis, and eccentric means connected with said bracket means for adjusting the angular position thereof about said axis.

8. An apparatus as defined in claim 6, wherein a first and a second set of tensioning rolls are disposed in the path of said stock ahead of and beyond said apparatus respectively frictionally engaged by said stock, and power means for rotating said first and second sets of tensioning rolls at differential velocities with said second set rotated at a higher velocity than that of said first set for imparting a prescribed elongation to said stock.

9. An apparatus as defined in claim 6 wherein a coldworking rolling mill is provided ahead of said apparatus engaged by said stock to impart a prescribed cold reduction thereto, and take-up coil means are provided beyond said apparatus for taking up the reduced and flattened stock.

10. An apparatus as defined in claim 6 wherein said leveler rolls have diameters in the range of about from 30 to 40 millimeters.

References Cited UNITED STATES PATENTS 9/1911 Abramsen 72164 5/1953 Maust 72162 

1. A METAL STRIP AND SHEET STOCK FLATTENING APPARATUS HAVING MEANS FOR FEEDING THE STOCK LONGITUDINALLY UNDER TENSION COMPRISING A SET OF AT LEAST TWO LEVELER ROLLS DISPOSED TRANSVERSELY OF THE STOCK AND ENGAGING OPPOSITE FACES THEREOF IN LONGITUDINALLY DISPLACED POSITIONS TO IMPART ALTERNATE TRANSVERSE FLEXING TO THE STOCK FOR REMOVING LONGITUDINAL DISTORTION THEREFROM, A CORRECTOR ROLL DISPOSED TRANSVERSELY OF THE STOCK BEYOND THE LAST LEVELER ROLL OF SAID SET ENGAGING THE FACE OF THE STOCK REMOTE FROM THE FACE ENGAGED BY SAID LAST LEVELER ROLL, MEANS FRO ADJUSTING THE POSITION OF SAID CORRECTOR ROLL IN A DIRECTION NORMAL TO THE PLANE OF THE STOCK TO SET UP DIFFERENTIAL TRANSVERSE STRESSES OVER THE THICKNESS DIMENSION OF THE STOCK IN A PATTERN SUBSTANTIALLY REVERSE FROM THE PATTERN OF TRANSVERSE STRESSES SET UP BY SAID LAST LEVELER ROLL TO CANCEL THE TRANSVERSE CAMBER THAT TENDS TO BE IMPARTED BY SAID LAST LEVELER ROLL TO THE STOCK 